4 years NCB is good right? I'd have thought that would be almost standard nation wide? Or me being naive thinking it is easy to get NCB...
4 years NCB at 21 is very good, as Chuff says very few 17 year olds can afford to have an insurance policy in their own name to build up NCB.
Combine that with some of the statistics floating around, e.g. 27% of 17-19 year old male drivers have a crash within the first year of driving, for someone to get to 21 without having an accident says a considerable amount about their driving.
That said, I'm 25 with 6 years NCB, the only reason it isn't 8 years is that I wasn't in a position to be able to insure a car at 17.
I say all credit to your brother for doing it while he can, as soon as he has to start paying a mortgage/rent and all the bills that come with moving away from home he might not be able to.